I served 8 years active duty from 2003-2011. Things may have changed since then, but at that time Military members have a couple of options. I will speak solely on the Army, as each separate forces may do it differently. 1, in their spare time they can take classes for free using tuition assistance(TA), paperwork signed by their company commander that allows them to take classes. This can be done online or in person and doesn’t affect their normally daily operations. They still go to work daily and work comes first. 2, when a soldier is in their reenlistment window sometimes and I do mean sometimes they will have the option to reenlist for X amount of years but part of the deal is they get what’s called a school opp. For 6 months the soldier will attend school in person or online. During this time the soldier goes to class like a normal civilian, doesn’t report to his/her military job. They do have to check in with a supervisor via phone, email etc once a week. They can be called in for (UA) urinalysis testing and any mandatory formations, but it’s mostly school only for those 6 months. Soldiers must remain in good standing GPA and grades wise with the school the entire time using both options. As well as good standing with the Army. Can not be flagged, No discipline problems, pass pt test etc. Obviously anyone can pay their own way through school. As far as post military eligibility after they have served, I have no idea. I would think it’s similar to someone taking a Mormon mission but I could be wrong.